August 23, 2006

Breeding Between the Lines

Alon Ziv presents evidence from academic journals, world history, pop culture, and recent census counts to prove that interracial individuals have significant physical and mental advantages. From the sex lives of bedbugs to the remarkable feats of professional athletes, he illustrates how biology influences every aspect of our lives and how the right combination of genes can make all the difference.

I have heard similar views before, and I have three main objections to this hypothesis. If you have read the book, and these objections are covered, feel free to comment.

My first objection is that humans tend to prefer individuals with physical traits similar to themselves. Research on human marriage patterns has established this fact. Therefore, people with average features will tend to be higher rated, because they are more similar to a larger number of people than outliers of phenotypic space. Hence, we would not expect that interracial people who inhabit an underpopulated region of phenotypic space to be highly rated from a group of judges drawn from the population as a whole.

My second objection is that interracial relationships do not occur uniformly in geographical and social space. It is also known that people's attractiveness and health also varies with geography and social class. Therefore, to assess the qualities of interracial individuals we must compare them against uniracial individuals from the same parental background, and not the general population of a particular country.

Thirdly, interracial individuals represent a wider range of phenotypes. In a sense, they represent novel chance combinations of genes from genetically distant populations. Whereas trait complexes are expected to be mostly harmonic within racial groups (since the dysharmonic combinations have been partially culled by evolution), traits inherited from different races may clash, presenting a dysharmonic phenotype. They may also match in an original way, including individuals of great beauty or other qualities. However, we should not judge the entirety of the interracial distribution by its right tail, e.g., the famous athletes, or celebrities of interracial background that we may be familiar with.

I feel like all of my recent posts have been about things I wish didn’t exist. :| I can’t believe this book is actually hitting the shelves. I remember being contacted by the author years ago in my capacity as Swirl’s Executive Director. Once I heard his premise, I refused participation.

4 comments:

I haven't read the book but I do recall my anthropology professor from the early '90s who made a similar observation concerning biraciality and its connections to better genes, higher intelligence, and evolutionary symmetry.

I'm no geneticist yet it makes perfect sense to me from a more subjective standpoint (see images below) as well as from purely logical standpoint.

Inbreeding tends to reinforce certain genetic traits which, over the course of time (if continously reinforced and re-circulated back into the gene-pool), would make the gene pool increasingly stagnant, leading to an increasingly assymetrical look.

Not to mention that marrying someone from the same gene pool or genetically similar increases the likelihood of having offspring who inherit two copies of deleterious recessive genes such as mental retardation.

I have a step-cousin down here in South Georgia who is that way (from inbreeding).

Your first objection, the fact that humans are not likely to mate with those who look different from themselves, doesn't necessarily invalidate Ziv's argument.

Naturally, factors such as distance, cultural taboos, social class, geography, evironment, lack of uniformity in interracial marriages, and a host of other factors could pose many difficulties for biraciality and evolutionary symmetry to arise. Yet a few of us do manage to exist in spite of the social rejection and insurmountable difficulties and odds.

Thus, your second objection seems irrelevent as well; as it refers strictly to non-hereditary factors whereas Ziv was arguing for the existence of hereditary factors that are involved in evolutionary symmetry.

Thirdly, a widest gene pool and a widest range of phenotypes is precisely what is necessary for biraciality and evolutionary symmetry: not the opposite. Your objection that traits inherited from different races may clash seems to be hypothetical at best or racist at worst, since the argument Ziv is making, from what I gather, is that heterogeneity promotes symmetry which results in more attractive appearances, not less attractive or clashing assymetrical features (see images below). At any rate, I'm not aware of any studies done to date on biraciality which could possibly support or refute your hypothesis or theory. I really don't think that science nor society has any scientific interest in knowing one way or the other, to be perfectly frank; yet thought I would respond to argue on my behalf.

First of all, regarding continuous traits such as intelligence, athleticism, etc. and mixed children having better traits than their pure bred colleagues is flat out wrong. What actually happens is that the mixed-raced child will fall in between the averages of the two races. For example, the IQ and GPA of mulatto children are between that of whites and blacks. Same could be said for other traits.

As far as subjectivity goes, please dont give links to celebrities, as that is a biased sample base to choose from (as to be a celebrity in the first place, you must be attractive). I can easily link more pictures of beautiful pure breeds.

Now, the reason why stagnancy occurs is that there's no evolutionary reason for it to change. So what if it remains stagnant? If the combo of traits back in the day still are advantageous now, then there shouldn't be changes. Outbreeding can also get rid of recessive traits that would be advantageous to have (such as sickle cell in a malaria filled region) just for the pure fact that these recessive alleles were naturally selected for that specific environment. And yes, the notion that some genes just dont mix well together and causes the offspring to be less fit is a valid one, because we see it in the animal kingdom all the time (Ligers and Mules).

One thing you dont mention about hybrid vigour is that hybrid vigour only applies to the F1 generation. After F1, out breeding depression kicks in and suddenly, the descendants of a mixed race union is actually less fit than their pure breed ones. I'll give you an example. It's possible for mixed children to inherit the recessive alleles of BOTH races. It will not be expressed of course. However, they are now carriers of it. You know what that means? F2 generation can now get BOTH of the race's deleterious recessive alleles expressed. This is precisely why farmers sterilize hybrids and never let them reproduce and this is only if the farmers even decide something like that. Most of the time, the risk of outbreeding depression DOES NOT outweigh the benefits from hybrid vigour. In fact, offsprings of hybrids (F2 and beyond) tend to be less stable than pure breeds.

In fact, there are studies that show that half mixed children are more delinquent than their pure-bred peers (but that could be due to social factors).

Now, I will present something to you that will pretty much destroy your whole argument of symmetry. Heterozygosity has almost ZERO correlation with symmetry.

Another high correlate of symmetry obviously would be that of canalization because canalization is essentially an organism's ability to develop symmetrically. What is canalization? It's an organism's ability to develop its races'/populations' phenotypes despite stress, be it environmental or biological; it can be equated to developmental stability. Guess what happens to phenotypes when outbreeding occurs? Genotypes and phenotypes are basically "mixed" so that anatomical features tend to deviate a lot from the features of BOTH parents. This can explain why hybrids can be less stable than their pure bred counterparts. If you want to know more about canalization and symmetry:http://www.amazon.com/Asymmetry-Developmental-Stability-Evolution-Ecology/dp/019854894X

So in turn, the crux of the argument is that interracial children are not more symmetrical (if even less), and hybrid vigour is iffy at best. Can we REALLY say that mixed children are better then? Probably no.

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